A tower crane anti-collision system is an operator support system for tower cranes on construction sites. It helps an operator to anticipate the risk of contact between the moving parts of a tower crane and other tower cranes and structures. In the event that a collision becomes imminent, the system can send a command to the crane's control system, ordering it to slow down or stop.[1] An anti-collision system can describe an isolated system installed on an individual tower crane. It can also describe a site wide coordinated system, installed on many tower cranes in close proximity.